TutrboDIESELtrooper is correct.
Go with the 4D55 as it is a direct replacement for the 2.6. I still think that rebuilding the 2.6 is similar to putting a candy apple paint job on a garbage truck. With a timing modification, my 2.3 out performed the Ford 4.0 and lasted 192,000+ miles.

87 Raizer, 4.3V6, Mod TH700R4,231CHD, detroit rear and LSD front, bouncy seats, 2" lift and 32x15 BFG MT tires.